This past May, in a major policy shift, the World Health Organization said electromagnetic fields produced by mobile phones are possibly carcinogenic. Although the International Association for the Wireless Telecommunication Industry says there’s no evidence that cell phones have a negative impact on health, many people are wondering exactly how electromagnetic fields, including those generated by cell phones, might harm them.

The World Health Organization says at least five billion people around the world use mobile phones and those who use them most frequently could be at risk for malignant brain tumors.

Many scientists welcomed the WHO statement, but some said it did not go far enough because it didn’t mention impacts on human health from cell towers and other wireless devices.

Camilla Reed is founder and director of ElectromagneticHealth.org, an advocacy group that’s been critical of the mobile phone industry. She explains the basics of electromagnetic fields.

“An electromagnetic field is a wave with a frequency. The frequency may be long or tight. It’s energy; it’s packets of energy that is a natural phenomenon on earth, but it is also modulated by mankind to create telecommunication spectrums that are artificial frequencies that are not found in nature and that our bodies are not adapted to,” Reed said.

Reed says research on the biological impact of electromagnetic fields goes back to the 1950s. Those impacts include not only cancer, but other effects on living cells and their genetic material, their DNA.

Reed is especially concerned about the growing pollution from electromagnetic fields near schools, like these cell phone antennas next to a high school football field in a Washington suburb.

Scientists disagree about the health effects of electromagnetic fields. But they all agree that caution should be used when it comes to children, the most vulnerable group.

Some health experts believe the effects could be wide-ranging. Dr. Ashok Agarwal heads the Center for Reproductive Medicine at Cleveland Clinic. He has done several studies on the impact of cell phone use on male fertility.

“We demonstrated that men who use cell phones for more than four hours per day have a significant reduction in their semen quality in most of the semen parameters such as sperm count, mobility, and morphology,” Agarwal said.

Dr. Agarwal says other scientists have gone farther in finding damage to DNA and other changes attributed to electromagnetic fields.

Neuroscientist Nora Volkov, at the National Institutes of Health, has been using magnetic resonance imaging ((MRIs)) to study human brain responses to electromagnetic fields.

“What our study does show is that the human brain is sensitive to the effects of electromagnetic radiation from cell phone exposure, when the cell phones are placed by the side of the head,” Volkov said.

Volkov’s study did not determine long-term impact. But she compares her initial studies to those done decades ago on the health effects of tobacco. She says scientists had to wait 15 to 30 years before there was conclusive evidence that smoking causes cancer.

On the safety of cell phones, scientists offer these suggestions. “When it comes to children and adolescents, I would give the recommendation to parents to encourage them not to use the cell phone by the side of the head but instead to use the speaker phone mode or with a wire, and certainly would not recommend for them to sleep with their cell phones under their pillows,” Volkov said.

Dr. Ashok Agarwal from Cleveland Clinic.

“The technology is very important for our day-to-day life, but we need to be aware that there may be some possible side effects that can be there with overuse of these technologies,” Agarwal said.

The evidence on the cancer-causing potential of cell phone radiation is not yet conclusive, but the World Health Organization’s cautionary stand is certain to fuel intensified research into electromagnetic fields and their impact on public health.